The invention generally relates to a screening or shielding apparatus for a generator producing radio-isotopes, particularly radio-isotope solution that can be used as a diagnostic agent adapted for intravenous administration. The generator typically used for this situation produces daughter radioactive isotopes from elution of parent isotopes within the generator. The generator, often referred to as a "cow", is constructed so that the user can at any desired instance draw at a tapping point on the generator a quantity of solution containing the radio-isotopes. A radio-isotope suitable for this purpose is Technetium 99 m (hereinafter referred to as 99 mTc) which is obtained from the parent isotope Molybdenum-99 (hereinafter 99 Mo) in a 99 mTc generator. Typically these generators are designed and configured to produce a sterile 99 mTc solution as a diagnostic. With the parent isotope present in the generator producing a high radiation intensity, extensive safety measures should be taken to shield the operator. For this purpose a lead screening jacket, or jacket of any other material preventing penetration of radioactive material, is employed to provide sufficient protection for storage and transport.
Typically such a generator is maintained for relatively long periods of time in that vicinity of a hospital or clinical laboratory where it finds its greatest use. Although the generator itself is surrounded by a screening jacket or shield, it has been found desirable to provide additional protection against radioactive radiation for the hospital or laboratory staff who are regularly in the direct proximity of the generator. For this purpose the generator is additionally surrounded by extra lead shielding device. Where the extra shielding material is employed, a tapping point for the eluent solution containing the radio-isotope diagnostic must be provided at a position readily accessible to the operators. If the eluent is outside the generator, the shield must also have an easily accessible connection point for the holder of eluent. These additional access means must include closure for the opening or openings of a material and configuration which will satisfactorily shield the users from the radiation produced. Such a closure is typically a lead stopper.
When the yield of radio-isotope obtained by elution becomes insufficient the generators must be replaced by a fresh one, in the case of a 99 mTc generator usually every one to two weeks. As a result, the shield must be constructed so that the generator can be readily replaced by a fresh one when the desired yield has been depleted. Shielding devices employed heretofore have included concentric lead rings which are covered on top by a lead coverplate. When the need to replace the generator arises, the lead cover and the lead rings are removed one by one to allow withdrawal of the old generator and replacement by a fresh generator. Once the fresh generator is in place the rings must be replaced again successively around the new generator. This laborious process unnecessarily exposes the operator to radioactive radiation for a relatively lengthy period of time.
Another shielding device has included a lead vessel having a lead cover which, after removal of the cover, allows the old generator to be lifted from the vessel and a fresh generator replaced. The problem with this approach is that it is rather awkward for the operator to accommodate this type of procedure. For example these lead vessels are typically maintained in a hospital or laboratory in a hooded enclosure area. Hence the space above the lead vessel is restricted severely impeding replacement of the generator. This is a problem which becomes even more acute when one appreciates that the generator is itself formed of lead shielding material and is of considerable weight. As a result when being lifted above the lead vessel in a restricted hood, the generator could easily slip from the operator's hands and cause serious radioactive accidents. Because the generator producing the radio-isotopes comprises a large quantity of radioactivity, should the generator be damaged and the radioactive material released, serious danger could result to the health and safety of those in the vicinity of such an accident.
Although some shielding devices avoid some of the problems discussed, they still have not proved to be completely satisfactory. Such devices include a 99 mTc generator commercially available under the tradename Stercow 99 M. This shield includes a lead base plate and a lead jacket extending vertically therefrom. The enclosure has a closeable opening to the tapping point for the solution containing the 99 mTc. The cylindrical lead jacket is divided into two substantially equal halves which can be moved relative to one another, as well as the base plate, in the lateral direction. The moving parts of the lead jacket are slideable on rails or slides provided on the base plate and have grips on either side of moveable parts to provide manual means for moving towards and away from one another. By moving the parts of the jacket apart, an opening is obtained sufficiently large to allow removal of the depleted generator and replacement by a fresh generator. Once the fresh generator is in place, the lead jacket halves are simply moved toward each other and substantially completely shield the generator.
Although this device may remove some of the disadvantages discussed above, there still remains the need for sufficient space in the lateral direction for this device to be operable. As generators are often placed in relatively small enclosed spaces there is typically little or no additional room to accommodate such lateral movements. In some countries administrative bodies, such as The Netherlands Ministry of Health, require a safe place which may include a hood or sterile cupboard. The loss of space which typically accompanies such a requirement is considerable and may preclude the use of a device such as the Stercow 99 M where the outside diameter of the jacket in the closed position is less than 30 centimeters, but in the moved apart condition the device occupies a width of 95 centimeters.
The invention described herein provides a shield for a generator producing radio-isotope solutions which overcomes the disadvantages of those shielding devices discussed above in connection with the prior art, including that of the Stercow 99 M. The screening device of the invention described herein includes a lead jacket extending vertically from a lead bottom portion. Access is provided in the shield to a tapping point for the solution containing radio-isotope. In addition, a closeable opening is provided in the lead jacket characterized by two parts of which one is stationary with respect to the bottom portion and the other is rotatable with respect to the bottom portion. The stationary portion of the jacket has an opening which is sufficiently large to provide passage therethrough of the generator. The rotatable or moveable portion also has an opening which is sufficiently large to provide passage therethrough of the generator and is rotatable between an open position where the openings register to permit passage of a generator and a closed position where the generator is completely covered. The rotatable portion is concentric with the stationary portion such that when in the open position the rotatable portion is substantially adjacent to the stationary portion and provides easy access to the generator.
With this invention the replacing of a depleted generator is substantially easier than those known heretofore. A generator can be placed within the screening device according to this invention by simply turning away the rotatable part of the jacket while maximizing effective use of space. In other words, unlike some of the devices described above, the shield apparatus of the subject invention can be moved between the open position for placing the generator within the device without requiring more space than the closed position. Specifically, as will be described in the preferred embodiment hereinafter, the screening device according to this invention would not occupy any more than 35 centimeters in either the open or closed position. Consequently, a considerable gain in space is obtained through the uses of the subject invention over those shielding devices of the prior art described above.
Of course the invention need not be cylindrical in configuration but rather can have a number of configurations so long as the general principle of concentricity and reduction in operating space is achieved. In some generators the eluent is contained in a separate holder outside of the generator. In this case the internal configuration of the shielding device is changed accordingly to accommodate this separate holder, and as a result, there is usually an extra closeable opening through which access is gained to the eluent holder from a position outside of the device. Such differences in operation and configuration of the generator can readily be accommodated by the subject invention.
The inventive screening device need not be restricted to use with a generator producing radio-isotopes; but rather may serve to store other radioactive products or materials. The invention will be described in greater detail with reference to the preferred embodiment shown in the accompanying drawings.